1. Field of the Invention
The present invention relates to a rotation angle detector, and in particular, to a novel improvement in which, in a variable reluctance (VR) type resolver using a rotor constructed solely of a core, with first and second annular stators being stacked together to cancel a deterioration in accuracy due to eccentricity, the positions of slots of the first and second annular stators are deviated from each other, whereby it is possible to form windings continuously around projected poles of the first and second stators by using a single winding apparatus, and it is possible to produce the rotation angle detector inexpensively by using conventional production equipment.
2. Description of the Related Art
As shown, for example, in Japanese Patent 3182493, in a rotation angle detector constructed of a conventionally used VR type resolver of this type, the core configurations of the annular stators are the same in the axial direction, that is, in the thickness direction, with a winding being wound around each projected pole.
With this construction, when the X-number, that is, the axial double angle, is large, the error in angle detection is small, and there is no problem for practical use. However, when the axial double number is small, that is, in the case, for example, of an axial double angle of 1X, an angular error of several tens of degrees is generated by little eccentricity.
To solve the problem of the angular error described above, there has been adopted a measure in which, as shown in Japanese Patent 3138606, a pair of resolvers adopting a pair of first and second annular stators are used and in which the first and second stators are stacked together, with the slot positions, that is, the projected pole positions being matched (coinciding with other), the windings (for excitation and 2-phase output) wound around the first and second annular stators being connected in series, whereby unbalance in the output voltage and angular error due to eccentricity are eliminated.
Further, as a measure for canceling the influence of eccentricity, there has been proposed a construction as shown in JP 07-043265 B, in which a pair of annular stators are used.
The conventional rotation angle detectors, constructed as described above, have the following problems.
That is, in the case of the construction of Japanese Patent 3138606, it is possible to cancel the influence of eccentricity, and the angular error in the case of 1X is significantly improved. However, since two independent resolvers are stacked together, it is necessary for the windings wound around the resolvers to be connected in series, so that the winding cannot be effected by a single winding operation.
Further, since a case and a shaft are required, the number of parts is doubled, resulting in an increase in cost. Further, due to the connection of the two resolvers, it is difficult to achieve a reduction in the axial length, that is, the thickness.
In the case of the construction disclosed in JP 07-043265 B, a pair of resolvers are combined so as to be stacked together as in the above case, so that the number of coil windings and stator parts and the number of assembly processes are large, making it difficult to achieve a reduction in cost.